Heterozygous protein-S deficiency: a study of a large kindred.

Another family with protein-S deficiency is described here. The defect is characterized by a reduced level of total protein-S antigen; in addition, a markedly reduced level of free protein-S antigen was found. We have studied 20 family members. Ten of them showed reduced levels of protein-S antigen. Five of the affected patients manifested 'thrombophilia'. All the symptomatic patients developed the first thrombotic event at a young age. Heparin and oral anticoagulants were useful for the treatment of the acute phase of the thrombotic events, and in 1 symptomatic patient, the life-long oral anticoagulation treatment was effective in preventing relapses. On the other hand, all the symptomatic but untreated family members developed several recurrent thrombotic episodes.